Automotive restraint systems, referred to as airbag module assemblies, are installed to protect the driver and other occupants from injury in the event of a collision. The airbag, activated by an ignitor, is rapidly filled with gas generated by the ignitor and is designed to inflate in approximately 50 milliseconds or less. The uninflated, folded airbag is mounted within a housing having a decorative cover which is designed to open for deployment of the inflating airbag.
Extreme pressures are generated by the explosive nature of the inflating airbag behind the cover, creating a difficult problem in installing the cover to the airbag housing in such a manner so as to prevent the cover from separating from the housing or breaking into pieces to thereby prevent those from becoming dangerous projectiles with respect to the vehicle occupants.
The prior art has resorted to a number of approaches for handling the aforesaid separation problem including anchoring the sidewalls of the cover to the housing by rivets, brackets or other structure. In one module cover attachment method, an outwardly and downwardly projecting lip on the housing must be inserted into a locking groove located on the inside of the vertical walls or locking blocks on the vertical wall of the cover. Assembling such a cover can be difficult as well as time consuming because the housing lip must be inserted in the locking groove on the inside of the cover. Such an assembly involves a relatively difficult process of bending and simultaneously pushing on the cover in order to spread apart the locking groove to insert the housing lip into the locking groove which is smaller in size than the lip. This attachment means is meant to prevent the cover from translating and/or rotating outward during deployment of the airbag since such deployment can generate pressures inside the cover of about 100 psi or more. The blocks of the vertical walls are meant to prevent the locking blocks from becoming disengaged from the lip of the airbag housing. However, experience has demonstrated that without further means to restrain the lower edge of the cover sidewall the cover groove can become disengaged from the housing lip. Therefore, additional retainer devices, such as brackets, rivets or the like have been installed in order to attempt to prevent separation of the lower edge of the cover sidewall from the housing from occurring on deployment of the airbag; otherwise, outward pressure against the cover sidewalls created by the inflating airbag will remove the housing lip from the groove and/or break the non-anchored lower ends of the sidewalls. In addition, the type of plastics which can be used for such a cover is limited and the molding thereof and removal of the cover from the mold is complicated because of the locking groove. Furthermore, a complicated mold design is required. Moreover, damage to the cover can occur quite often during removal of the cover from the mold and said removal undesirably requires hand removal.